Electricity: conductors and insulators – Boxes and housings – With grounding means
Reexamination Certificate
2000-08-10
2001-12-11
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
With grounding means
C174S0400CC, C174S006000, C174S135000, C174S078000, C439S092000, C439S098000, C361S799000
Reexamination Certificate
active
06329592
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to devices for implementing a ground connection between an electrical meter box and a common ground point. More particularly, the present invention relates generally to clamp devices which mount to an electrical meter box and connect via a flexible conductor with a common ground point.
A number of various types of devices have been employed for connecting a ground wire with an electrical meter box. Most conventional devices employ clamp assemblies of various forms. In applications to which the present invention relates, the connecting devices are ordinarily clamped onto the exterior of the electrical meter box which is mounted on the wall of a building.
A number of conventional designs are configured to mount rigidly or semi-rigidly onto the electrical meter box. For such designs, damage to the electrical meter box can occur when the clamping force is applied to the electrical meter box. For example, it is not uncommon for the electrical meter box to be bent or twisted when the clamping force is applied.
In another known design, the device clamps onto a corner of the electrical meter box. A lower flange of the device engages a bottom skirt of the electrical meter box top cover. A bolt theadably disposed through a top plate of the device engages the electrical meter box top cover. Applying a torque to the bolt causes the device to be clamped to the electrical meter box. Such devices may not provide an adequate electrical connection with the electrical meter box.
SUMMARY OF THE INVENTION
Briefly stated, the invention in a preferred form is a ground clamp for connecting the metallic enclosure of an electrical meter box with a ground conductor. The ground clamp comprises a U-shaped clamp member, a bolt member, and means for mounting the ground conductor. The clamp member has first and second legs which define a slot for receiving an edge portion of the meter box enclosure. The first leg has a pair of fingers which are separated from a center segment by a pair of openings. The edge portion of the meter box enclosure is resiliently clamped between the fingers and the second leg. The center segment includes a socket having an inner surface, at least a portion of which has a thread. The bolt member has a stud portion extending from the distal end and a bolt head portion extending from the proximal end. At least one protrusion extends axially from the distal end to a sharp edge. The stud portion includes a threaded segment disposed proximate the distal end and an unthreaded shaft segment disposed intermediate the threaded segment and the bolt head portion. The stud portion of the bolt member is mounted in the socket of the clamp member such that the shaft segment is positioned in the threaded portion of the socket and the threaded segment is positioned within the slot when the sharp edge of the protrusion contacts the exterior surface of the edge portion received within the slot. The sharp edge of the protrusion removes the corrosion inhibiting coating from the exterior surface of the edge portion to electrically connect the meter box to the clamp without deforming the meter box enclosure upon rotation of the bolt member.
The fingers and the second leg of the clamp member define a first gap and the center segment and the second leg of the clamp member define a second gap, where the width W
3
of the second gap is greater than the width W
1
of the first gap. The widths of the first and second gaps are selected such that W
1
is less than the thickness T
1
of the metal forming the edge portion of the meter box enclosure and W
3
is greater than T
1
. Therefore, the edge portion of the meter box enclosure is clamped between the fingers and second leg and a gap (having a width W
2
) remains between the center segment and the exterior surface of the edge portion. Preferably, for an edge portion having the minimum thickness allowed by manufacturing tolerances (T
1
min
), W
2
=W
3
−T
1
min
.
The socket has a height H
1
, the thread of the socket has a length L
1
, and the threaded segment has a length L
2
, where L
2
≈W
2
+(H
1
−L
1
). The socket may have an unthreaded portion disposed adjacent the slot. In this case, the unthreaded portion has a length L
4
, where L
4
=H
1
−L
1
.
The meter box ground clamp may also include a gel-filled boot which provides a water-tight seal with the exterior surface of the meter box enclosure to prevent corrosion of the edge portion of the meter box enclosure from which the corrosion inhibiting coating has been removed.
To establish a ground connection using the meter box ground clamp described above, the second leg of the clamp member within a seam of the meter box enclosure such that the edge portion of the meter box enclosure is received within the slot of the clamp member and is clamped between the fingers and second leg. A torque is applied to the bolt member until the sharp edge of the protrusion contacts the exterior surface of the edge portion. At this point any forces imposed by the bolt member on the meter box enclosure are resiliently absorbed by flexing the center segment or the second leg of the clamp member. Additional torque is applied to the bolt member until the sharp edge of the protrusion removes the corrosion inhibiting coating from the exterior surface of the edge portion. The ground wire is then mounted to the meter box ground clamp.
To seal the connection between the meter box ground clamp and the meter box enclosure, a gel-filled boot may be clamped between the ground wire and the surface of the edge portion of the meter box enclosure. The gel-filled boot is installed by inserting the bolt head portion of the bolt member through an opening in the gel-filled boot after the corrosion inhibiting coating has been removed from the exterior surface of the edge portion. Mounting the ground wire to the meter box ground clamp compresses the boot, biasing the boot into sealing engagement with the surface of the meter box enclosure.
An object of the invention is to provide a new and improved ground clamp for implementing a ground connection between an electrical meter box and a common ground point.
Another object of the invention is to provide a new and improved ground clamp for use with an electrical meter box that will not damage the box or the box finish.
A further object of the invention is to provide a new and improved ground clamp which is inexpensive to manufacture.
Other objects and advantages of the invention will become apparent from the drawings and specification.
REFERENCES:
patent: 5160271 (1992-11-01), Franks, Jr.
patent: 5928006 (1999-07-01), Franks, Jr.
patent: 6118071 (2000-09-01), Munch et al.
patent: 6188020 (2001-02-01), Osterbrock et al.
patent: 2194860 (1988-03-01), None
Alix Yale & Ristas, LLP
Electric Motion Company, Inc.
Patel Dhiru R
Reichard Dean A.
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